Wire harnesses in which electrical connectors are connected to flat cables, including flexible circuit boards (FPC), have been used in the past mainly in electronic devices such as personal computers. In recent years, however, there has been an increasing demand for the use of such wire harnesses for the connection to controllers in the automotive field or the like.
For example, wire harnesses in which electrical connectors are connected to flat cables are used for the connection to automotive transmission controllers. In such cases, installation involves pulling an electrical connector connected to the end portion of a flat cable out of an opening in the transmission case.
In such cases, when a multipole connector in which a plurality of contacts are arranged in multiple rows is used as an electrical connector, the size of the electrical connector is increased, so that the opening bored in the transmission case is also inevitably increased. In order to solve this problem, a method is conceivable in which a plurality of stackable connectors each having a plurality of contacts arranged in a single row are prepared, the plurality of connectors are connected to the end portion of a flat cable, the individual connectors are successively pulled out through a relatively small opening bored in the transmission case, and the individual connectors are subsequently stacked up and integrated.
The connector shown in FIGS. 12 and 13A to 13C (see JP10-74541A), for example, is a known stackable connector in which a plurality of contacts are arranged in a single row. FIG. 12 is a perspective view of the upper-stage, middle-stage, and lower-stage base housings and FIGS. 13A to 13C are explanatory diagrams of such a conventional connector assembly.
This connector 101 shown in FIG. 12 comprises upper-stage, middle-stage, and lower-stage base housings 110a, 110b, and 110c, and a plurality of contacts 120 (see FIGS. 13A to 13C) inserted in the respective base housings 110a, 110b, and 110c. 
A plurality of contact receiving cavities 111 in a single row having the upper surfaces thereof open are formed in the upper-stage base housing 110a, and a cover body 115 that covers the upper surfaces of the contact receiving cavities 111 is integrally formed and joined by hinges 115a to the upper-stage base housing 110a. A pair of locking projections 116 are formed at either end of the cover body 115, and a pair of locking recesses 114 with which the locking projections 116 are locked are formed in either side wall of the base housing 110a. 
Furthermore, a plurality of contact receiving cavities 111 in a single row having the upper surfaces thereof open are also formed in the middle-stage base housing 110b. 
Moreover, a plurality of contact receiving cavities 111 in a single row having the upper surfaces thereof open are likewise formed in the lower-stage base housing 110c. 
In addition, the upper-stage, middle-stage, and lower-stage base housings 110a, 110b, and 110c are arranged so that these base housings 110a, 110b, and 110c are linked in a staircase like pattern with the upper surfaces of the contact receiving cavities 111 in each of the base housings 110a, 110b, and 110c. The upper-stage and middle-stage base housings 110a and 110b are linked by a frangible thin part 117a, the middle-stage and lower-stage base housings 110b and 110c are linked by a frangible thin part 117b, and these upper-stage, middle-stage, and lower-stage base housings 110a, 110b, and 110c are formed integrally from an insulative material. Furthermore, these base housings 110a, 110b, and 110c are constructed so that the middle-stage base housing 110b can be stacked on top of the lower-stage base housing 110c, and so that the upper-stage base housing 110a can be stacked on top of the middle-stage base housing 110b. A pair of locking projections 112 are formed on the bottom wall of the middle-stage base housing 110b, and a pair of locking recesses 113 are formed in either side wall of the lower-stage base housing 110c to engage the locking projections 112 when the middle-stage base housing 110b is stacked. Likewise, a pair of locking projections 112 are formed on the bottom wall of the upper-stage base housing 110a, and a pair of locking recesses 113 are formed in either side wall of the middle-stage base housing 110b to engage the locking projections 112 when the upper-stage base housing 110a is stacked.
As is shown in FIG. 13A, when assembling the connector 101, the contacts 120 are first inserted into the contact receiving cavities 111 of the respective base housings 110a, 110b, and 110c, and individual electrical wires W are connected by Insulation Displacement Connection (IDC) to the respective contacts 120 in this state.
Next, as is shown in FIG. 13B, the thin part 117a that links the upper-stage base housing 110a and middle-stage base housing 110b and the thin part 117b that links the middle-stage base housing 110b and lower-stage base housing 110c are cut.
Finally, as is shown in FIG. 13C, the middle-stage base housing 110b is stacked on top of the lower-stage base housing 110c, and the upper-stage base housing 110a is stacked on top of the middle-stage base housing 110b. Subsequently, the cover body 115 provided on the upper-stage base housing 110a is pivoted in the direction of arrow A shown in FIG. 12 to cover the upper surfaces of the respective contact receiving cavities 111. As a result, the connector 101 is completed.
With this connector 101, since a plurality of base housings 110a, 110b, and 110c are formed by a single molding process as one linked body, the number of parts can be reduced, and the work efficiency can be increased as a result of the simplification of the parts.
In the connector 101 shown in FIGS. 12 and 13A to 13C, individual electrical wires W are connected by IDC to the respective contacts 120, but it would also be possible to connect the end portion of a flat cable to the respective contacts 120. Furthermore, if the thin parts 117a and 117b are cut following the connection of the flat cable to the respective contacts, the individual base housings 110a, 110b, and 110c are pulled out of the opening in the transmission case, and the individual base housings 110a, 110b, and 110c are subsequently stacked up, then the opening in the transmission case or the like can be made smaller.
However, in the case of the connector 101 shown in FIGS. 12 and 13A to 13C, while arranging the wire harness, it is necessary to cut the thin parts 117a and 117b that are provided in order to form a plurality of base housings 110a, 110b, and 110c as one linked body in a single molding process. Therefore, there is a problem in that arranging the wire harness becomes troublesome.
Furthermore, in cases where the number of contacts 120 is increased or decreased in the connector 101, the number of base housings must be increased or decreased. However, since thin parts that link adjacent base housings are present, the degree of freedom in the housing construction is low, and a new mold for molding base housings is required in such cases, so that manufacturing is complicated, and there is a concern of increased cost.